[dpdk-dev] Instability of port ids

Stephen Hemminger stephen at networkplumber.org
Fri May 17 20:46:40 CEST 2019

Several customers have reported similar issues with how the owned/stack device model
works in DPDK. With failsafe/tap and VF or netvsc and VF there are DPDK ports which
are marked as owned and therefore not visible.

The problem is the application has to guess and workaround these port values in
the port mask that gets passed in on command line. This means a working application
has to modify its startup script to run on Azure. Worse the actual port values
change based on the number of NIC's configured.

Overall this is a nuisance for users. The whole DPDK port index concept is a bad
design. In Linux/BSD there is ifindex, but few applications care, they all use names
which is better. Very very few application care that eth1 is ifindex 4.

The whole assignment of ports is a mess as well since it is based on probe order
and that is based on PCI order, and not anything dependable. It gets worse with
command line arguments, vdev, owned devices etc.

All I can think of is that:
  * DPDK network devices need to have human readable names. current PCI is not good.
  * The names need to be repeatable/persistent. udev names are probably better than anything so far.
    Or bsd style names but they end up being device dependent.
  * The API to get from name to port needs to easy to use and the preferred method.
  * All examples and documentation should avoid using port index directly.
    You need port for fast rx/tx but setup should be by name.

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